1. Field of the Invention
The present invention relates to a new phosphoric ester compound and, more particularly, to a phosphoric ester compound containing a polyester chain useful as a pigment dispersant or flushing agent in the production of a pigment composition useful as a coloring material such as paint, printing ink, or a synthetic resin colorant.
2. Description of the Prior Art
In the conventional process for producing paints and printing inks, lecithin, which is one of phospholipids, has been used both as a dispersant for dispersing a pigment into a paint vehicle or printing ink varnish, and as a flushing agent for flushing the aqueous filter cake into an oil vehicle or oil varnish.
Being a natural phospholipid, lecithin is liable to oxidation and rancidity which lead to deterioration and putrefaction. Thus there has been a demand for a dispersant or flushing agent which is stabler and better than lecithin.
In view of the above-mentioned drawbacks of the conventional dispersant or flushing agent and in order to develop a new compound which is compatible with vehicles and varnishes and also with pigments and is useful as a pigment dispersant, the present inventors carried out a series of researches which led to the finding that a phosphoric ester obtained by reacting a polyester having a hydroxyl group with phosphoric acid exhibits outstanding properties and effects required for pigment dispersants. The present invention was completed based on this finding.